make rtengine::processImage return an Imagefloat instead of an Image16

This is for supporting saving to 32-bit float TIFFs

rtengine/imagefloat.h

@@ -106,6 +106,7 @@ public:
     void                 calcCroppedHistogram(const ProcParams &params, float scale, LUTu & hist);
 
     void                 ExecCMSTransform(cmsHTRANSFORM hTransform);
+    void                 ExecCMSTransform(cmsHTRANSFORM hTransform, const LabImage &labImage, int cx, int cy);
 };
 
 }